Half a croissant, on a plate, with a sign in front of it saying '50c'
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Rain-Dependent Variable Speed Limit Sign

Combine a rain guage with a variable speed limit sign
  (+19, -1)(+19, -1)
(+19, -1)
  [vote for,

I often become frustrated with the fact that many drivers seem to drive even faster in the wet weather than they do in dry conditions! Certainly it is considered wise to slow down significantly in wet weather, but road authorities are not easily able to legally enforce such recommendations.

That's where the Rain-Dependent Speed Limit Sign comes in. It's basically your standard electronic variable speed limit sign (which can be found in most major cities I wager) combined with a rain guage. Using a simple formula, the speed limit is progressively lowered based on the amount of rain caught by the rain guage. Moderate rain, for example, may result in a 10km/h drop, whereas a torrential downpour may see a 20-25km/h drop.

The result is a a legally-enforcable safer speed limit for wet conditions, saving lives and reducing insurance premiums.

Achenar, Oct 11 2004

Dynamic Speed Limits http://www.halfbake...ic_20Speed_20Limits
related idea [krelnik, Oct 12 2004]

New Jersey Turnpike info http://www.nycroads.../roads/nj-turnpike/
About halfway down: "An automatic traffic surveillance and control system provides information to the Turnpike Traffic Operations Center in New Brunswick from 965 imbedded sensors, as well as from closed-circuit TV cameras. Using this information, the system controls changeable message signs...and speed limit signs. The system alerts motorists to congestion, accidents and adverse weather conditions ahead." [krelnik, Oct 12 2004]


       Good idea! I also think this would help to reassure people who drive dangerously *slowly* in inclement weather. Elderly and new drivers who aren't sure what a safe speed is would be able to see that slowing, for instance, by 10 MPH is sufficient.
contracts, Oct 11 2004

       As an addition, you might think about higher fines during inclement weather, similar to what they do in work zones.
shapu, Oct 11 2004

       "Too fast for conditions" is a citeable violation in my state.
bristolz, Oct 11 2004

       In the UK, motorways have variable speed limits used to slow traffic in case of fog or congestion ahead. These are set from a central control point which also watches most sections of road via CCTV. Automated versions would be easily bakeable and effective if linked to the ubiquitous 'speed cameras' which photograph speeding drivers. [+]
wagster, Oct 11 2004

       In France they have ordinary speed limit signs with two posted speeds, one with a picture of a cloud and rain beside it.   

       Though this idea takes out the subjective appraisal of conditions by the driver.   

scubadooper, Oct 11 2004

       Same here, [bris]. [+]
Letsbuildafort, Oct 12 2004

       I thought about this very idea the other day, but I had extended it to account for all sorts of road conditions, including traffic at upcoming destinations etc. Basically all sorts of things would have to be monitored with tons of sensors active on every road at all times; then a sophisticated system of wire and wireless technology would have to be employed to get all of the sensor data to a central computer which would then set speed limits, traffic lights, etc. in an effort to optimize traffic flow. The central computer itself would talk to other central computers if a large city is to be integrated. Small towns and rural areas could be covered by fewer computers, obviously.
Size_Mick, Oct 12 2004

       "Too fast for conditions" is at least partly subjective. This would eliminate the ambiguity. [+]
yabba do yabba dabba, Oct 12 2004

       I think they are manually operated, not automatic, but the New Jersey Turnpike has lighted speed limit signs that are adjusted downward during bad weather.
krelnik, Oct 12 2004

       The sign (or a central computer such as the one [Size_Mick] suggests) would have to keep a log of the changes in the speed limit and weather conditions which caused it to change. If someone is caught speeding, they have to have a record, don't they?
rgovostes, Oct 12 2004

       Difficult to implement in rural areas, but then again, most improvements are. My hometown was still working on good signage and halfway sensible intersections as of the year of my departure.
RayfordSteele, Oct 12 2004

       Rather then a rain-catching gauge how about a sensor. Some cars have a rain sensor on the windscreen which automatically turns on the wipers when it rains. Using this system the signs could tell when it _wasn't_ raining and increase the speed into the normal range again.
Nontaigne, Oct 13 2004

       [nontaigne] That might not be enough. When the roadway is still wet, we probably want the lower speed to remain in effect for a little while, especially if we had a short rain after a long period of dry weather.
gardnertoo, Jul 13 2006

       Sounds pretty simple. After the rain, have a timed delay before the speed changes back. I'm wondering if we could get it to reduce the speed significantly right when the rain stops, and all the oil is still washing off the road...
ye_river_xiv, Jul 13 2006

       So, so many variables, including vehicle's tyres, suspension, weight distribution and acceleration/braking power. If a sign displayed a reduced speed limit, then someone slid off a corner due to non-wet weather tyres, or their vehicle simply not being as suited for wet conditions, (offroad tyres, for instance, that are useless on wet bitumen), they could possibly have grounds to sue. You are telling them it's okay to do the posted [reduced] speed limit.   

       Maybe if combined with WET ROAD MAXIMUM ALLOWABLE SPEED XXXX DRIVE WITH CAUTION or something similar. I just think that at present everyone accepts that they have to slow down in the wet, and [even if they are irresponsible drivers] are forced to err on the side of caution. If you post a new limit, they will take this as gospel, and not think about the road conditions, large puddles [aquaplaning] etc reduced visibility, etc.
Custardguts, Jul 14 2006

       Aw hell, this is all too complicated. Let's all go back to the good ol' days of horse and carriage. Enjoy the scenery for once, in the rain no less.   

       Oh MY Gawd! I said a "Let's all.." May Jutta forgive me, for I have sinned...
NotTheSharpestSpoon, Jul 14 2006


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